A new series of nucleoside analogs will be prepared. Each compound will have an exocyclic double bond, either directly linked to the furanose ring as an enol ether, or as a completely separated functional group. The base in most cases will be adenine. Other structural changes proposed for the new compounds involve the anomeric position and the configuration at various carbon atoms. The antibiotic, decoyinine, posseses an exocyclic double bond. Some of the compounds already prepared have demonstrated biological activity and it is possible that they are active as decoyinine analogs. All of the new nucleosides will be assayed as potential antitumor and antimicrobial agents. The synthesis of the new compounds will be somewhat novel. The main route includes the prior preparation of unsaturated carbohydrate derivatives and coupling of these to a suitable nitrogenous base, usually chloromercuri-6-benzamidopurine. The other route consists of the preparation of a suitable halosugar, then preparation of the nucleoside. In most cases the reactive halomethyl group will be in a configuration which will preclude cyclonucleoside formation during the elimination reaction to prepare the unsaturated nucleoside; otherwise the N-benzoyl group of adenine will be retained to prohibit cyclonucleoside formation during this step.